The present invention relates to the field of optical imaging in which objects which diffuse light, such as some human body tissues, are imaged using signals resulting from the injection of light into the object and detection of the diffusion of the light in the object at a number of positions. More particularly, the present invention relates to the choice of wavelengths for multiwavelength optical imaging in order to provide enhanced information.
Time-domain optical medical images show great promise as a technique for imaging breast tissue, as well as the brain and other body parts. The objective is to analyze the temporal point spread function (TPSF) of an injected pulse as it is diffused in the tissue, and the information extracted from the TPSF is used in constructing a medically useful image.
For example, one can extract time-gated attenuation information from the TPSF which improves the image spatial resolution over previous continuous wave methods. However, it is unclear whether such improvements in image spatial resolution are adequate for diagnosing breast cancer based on morphology.
An alternative approach is to use the TPSF to decouple the light attenuation into absorption and scattering components. This extra information, which cannot be obtained from continuous wave methods, may be clinically useful. Moreover, one can obtain the tissue absorption spectrum by performing time-domain measurements at multiple wavelengths. In tissue there are several molecules which absorb the light and are known as chromophores. Spectroscopic analysis of the tissue absorption spectrum permits chromophore concentrations to be measured. Furthermore, combination of the chromophore concentrations can yield physiological information, as opposed to morphologic information, which could provide a more medically useful image.
The problem is one of knowing which are the dominant chromophores to include in a tissue model and then choosing the xe2x80x9cbestxe2x80x9d wavelengths to deduce their concentrations most accurately.
It is an object of the present invention to provide an objective method for choosing the wavelengths for a multiwavelength TPSF-based optical imaging approach. For a given set of chromophores, the best selection of the wavelengths is performed for the set as a whole as opposed to choosing the best wavelength for each chromophore individually. Furthermore, hardware constraints can be taken into consideration in order to optimize the selection of wavelengths for a given device. Thus in one embodiment of the invention the method comprises selecting a set of chromophores for characterizing a property of the turbid media; defining parameters of the system including at least a number of the discrete wavelengths, a value of each of the wavelengths, source power and detector aperture for each of the wavelengths, a choice of image algorithm and source/detector geometries, a choice of source and detector and noise characteristics; fixing a value of all of said parameters except a plurality of said parameters values to be optimized; and determining an optimal value for each of said parameter values to be optimized as a function of a performance of the system in measuring a concentration of the chromophores in the turbid media for characterizing the property as a whole.